noapic [SMP,APIC] Tells the kernel to not make use of any
IOAPICs that may be present in the system.
+ nokaslr [X86]
+ Disable kernel base offset ASLR (Address Space
+ Layout Randomization) if built into the kernel.
+
noautogroup Disable scheduler automatic task group creation.
nobats [PPC] Do not use BATs for mapping kernel lowmem
Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
it has been loaded at and the compile time physical address
- (CONFIG_PHYSICAL_START) is ignored.
+ (CONFIG_PHYSICAL_START) is used as the minimum location.
-# Relocation on x86-32 needs some additional build support
+config RANDOMIZE_BASE
+ bool "Randomize the address of the kernel image"
+ depends on RELOCATABLE
+ depends on !HIBERNATION
+ default n
+ ---help---
+ Randomizes the physical and virtual address at which the
+ kernel image is decompressed, as a security feature that
+ deters exploit attempts relying on knowledge of the location
+ of kernel internals.
+
+ Entropy is generated using the RDRAND instruction if it
+ is supported. If not, then RDTSC is used, if supported. If
+ neither RDRAND nor RDTSC are supported, then no randomness
+ is introduced.
+
+ The kernel will be offset by up to RANDOMIZE_BASE_MAX_OFFSET,
+ and aligned according to PHYSICAL_ALIGN.
+
+config RANDOMIZE_BASE_MAX_OFFSET
+ hex "Maximum ASLR offset allowed"
+ depends on RANDOMIZE_BASE
+ default "0x10000000"
+ range 0x0 0x10000000
+ ---help---
+ Determines the maximal offset in bytes that will be applied to the
+ kernel when Address Space Layout Randomization (ASLR) is active.
+ Must be less than or equal to the actual physical memory on the
+ system. This must be a power of two.
+
+# Relocation on x86 needs some additional build support
config X86_NEED_RELOCS
def_bool y
- depends on X86_32 && RELOCATABLE
+ depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
config PHYSICAL_ALIGN
hex "Alignment value to which kernel should be aligned"
- default "0x1000000"
+ default "0x200000"
range 0x2000 0x1000000 if X86_32
range 0x200000 0x1000000 if X86_64
---help---
VMLINUX_OBJS = $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
$(obj)/string.o $(obj)/cmdline.o $(obj)/early_serial_console.o \
- $(obj)/piggy.o $(obj)/cpuflags.o
+ $(obj)/piggy.o $(obj)/cpuflags.o $(obj)/aslr.o
$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
--- /dev/null
+#include "misc.h"
+
+#ifdef CONFIG_RANDOMIZE_BASE
+
+unsigned char *choose_kernel_location(unsigned char *input,
+ unsigned long input_size,
+ unsigned char *output,
+ unsigned long output_size)
+{
+ unsigned long choice = (unsigned long)output;
+
+ if (cmdline_find_option_bool("nokaslr")) {
+ debug_putstr("KASLR disabled...\n");
+ goto out;
+ }
+
+ /* XXX: choose random location. */
+
+out:
+ return (unsigned char *)choice;
+}
+
+#endif /* CONFIG_RANDOMIZE_BASE */
#include "misc.h"
-#ifdef CONFIG_EARLY_PRINTK
+#if CONFIG_EARLY_PRINTK || CONFIG_RANDOMIZE_BASE
static unsigned long fs;
static inline void set_fs(unsigned long seg)
addl %eax, %ebx
notl %eax
andl %eax, %ebx
-#else
- movl $LOAD_PHYSICAL_ADDR, %ebx
+ cmpl $LOAD_PHYSICAL_ADDR, %ebx
+ jge 1f
#endif
+ movl $LOAD_PHYSICAL_ADDR, %ebx
+1:
/* Target address to relocate to for decompression */
addl $z_extract_offset, %ebx
leal boot_heap(%ebx), %eax
pushl %eax /* heap area */
pushl %esi /* real mode pointer */
- call decompress_kernel
+ call decompress_kernel /* returns kernel location in %eax */
addl $24, %esp
/*
* Jump to the decompressed kernel.
*/
xorl %ebx, %ebx
- jmp *%ebp
+ jmp *%eax
/*
* Stack and heap for uncompression
addl %eax, %ebx
notl %eax
andl %eax, %ebx
-#else
- movl $LOAD_PHYSICAL_ADDR, %ebx
+ cmpl $LOAD_PHYSICAL_ADDR, %ebx
+ jge 1f
#endif
+ movl $LOAD_PHYSICAL_ADDR, %ebx
+1:
/* Target address to relocate to for decompression */
addl $z_extract_offset, %ebx
addq %rax, %rbp
notq %rax
andq %rax, %rbp
-#else
- movq $LOAD_PHYSICAL_ADDR, %rbp
+ cmpq $LOAD_PHYSICAL_ADDR, %rbp
+ jge 1f
#endif
+ movq $LOAD_PHYSICAL_ADDR, %rbp
+1:
/* Target address to relocate to for decompression */
leaq z_extract_offset(%rbp), %rbx
movl $z_input_len, %ecx /* input_len */
movq %rbp, %r8 /* output target address */
movq $z_output_len, %r9 /* decompressed length */
- call decompress_kernel
+ call decompress_kernel /* returns kernel location in %rax */
popq %rsi
/*
* Jump to the decompressed kernel.
*/
- jmp *%rbp
+ jmp *%rax
.code32
no_longmode:
free(phdrs);
}
-asmlinkage void decompress_kernel(void *rmode, memptr heap,
+asmlinkage void *decompress_kernel(void *rmode, memptr heap,
unsigned char *input_data,
unsigned long input_len,
unsigned char *output,
free_mem_ptr = heap; /* Heap */
free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
+ output = choose_kernel_location(input_data, input_len,
+ output, output_len);
+
+ /* Validate memory location choices. */
if ((unsigned long)output & (MIN_KERNEL_ALIGN - 1))
error("Destination address inappropriately aligned");
#ifdef CONFIG_X86_64
parse_elf(output);
handle_relocations(output, output_len);
debug_putstr("done.\nBooting the kernel.\n");
- return;
+ return output;
}
#endif
-#ifdef CONFIG_EARLY_PRINTK
-
+#if CONFIG_EARLY_PRINTK || CONFIG_RANDOMIZE_BASE
/* cmdline.c */
int cmdline_find_option(const char *option, char *buffer, int bufsize);
int cmdline_find_option_bool(const char *option);
+#endif
-/* early_serial_console.c */
-extern int early_serial_base;
-void console_init(void);
+#if CONFIG_RANDOMIZE_BASE
+/* aslr.c */
+unsigned char *choose_kernel_location(unsigned char *input,
+ unsigned long input_size,
+ unsigned char *output,
+ unsigned long output_size);
#else
+static inline
+unsigned char *choose_kernel_location(unsigned char *input,
+ unsigned long input_size,
+ unsigned char *output,
+ unsigned long output_size)
+{
+ return output;
+}
+#endif
+#ifdef CONFIG_EARLY_PRINTK
/* early_serial_console.c */
+extern int early_serial_base;
+void console_init(void);
+#else
static const int early_serial_base;
static inline void console_init(void)
{ }
-
#endif
#endif
projects / cascardo / linux.git / commitdiff